Reproducible Research Statement:Study protocol: Available in German from Dr. Lennerz (e-mail, lennerz@dhm.mhn.de). Statistical code: Not available. Data set: Available from Dr. Lennerz (e-mail, lennerz@dhm.mhn.de).

Background: Cardiac implantable electronic devices (CIEDs) are considered standard care for bradycardia, tachycardia, and heart failure. Electromagnetic interference (EMI) can disrupt normal function of these devices and may cause pacing inhibition, inappropriate shock delivery, or device reprogramming. Electric cars represent a potential source of EMI. However, data are insufficient to determine their safety or whether their use should be restricted in patients with CIEDs.

Methods and Findings: We approached 150 consecutive patients with CIEDs seen in our electrophysiology clinic for routine follow-up between May 2014 and January 2015; 40 patients declined to participate, and 2 withdrew consent. Exclusion criteria were suspected lead malfunction or CIED battery life less than 3 months. After we obtained informed consent, CIED programming was optimized to detect EMI according to established protocols (1). Participants were assigned to 1 of 4 electric cars with the largest European market share. To ensure electric operation only and maximum electromagnetic field generation, we excluded hybrid vehicles. Car assignment was determined by vehicle availability when participants visited the test facility.